001 /*
002 * Copyright 1994-2005 Sun Microsystems, Inc. All Rights Reserved.
003 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004 *
005 * This code is free software; you can redistribute it and/or modify it
006 * under the terms of the GNU General Public License version 2 only, as
007 * published by the Free Software Foundation. Sun designates this
008 * particular file as subject to the "Classpath" exception as provided
009 * by Sun in the LICENSE file that accompanied this code.
010 *
011 * This code is distributed in the hope that it will be useful, but WITHOUT
012 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
013 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
014 * version 2 for more details (a copy is included in the LICENSE file that
015 * accompanied this code).
016 *
017 * You should have received a copy of the GNU General Public License version
018 * 2 along with this work; if not, write to the Free Software Foundation,
019 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
020 *
021 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
022 * CA 95054 USA or visit www.sun.com if you need additional information or
023 * have any questions.
024 */
025
026 package java.io;
027
028 /**
029 * A <code>ByteArrayInputStream</code> contains
030 * an internal buffer that contains bytes that
031 * may be read from the stream. An internal
032 * counter keeps track of the next byte to
033 * be supplied by the <code>read</code> method.
034 * <p>
035 * Closing a <tt>ByteArrayInputStream</tt> has no effect. The methods in
036 * this class can be called after the stream has been closed without
037 * generating an <tt>IOException</tt>.
038 *
039 * @author Arthur van Hoff
040 * @version 1.53, 05/05/07
041 * @see java.io.StringBufferInputStream
042 * @since JDK1.0
043 */
044 public class ByteArrayInputStream extends InputStream {
045
046 /**
047 * An array of bytes that was provided
048 * by the creator of the stream. Elements <code>buf[0]</code>
049 * through <code>buf[count-1]</code> are the
050 * only bytes that can ever be read from the
051 * stream; element <code>buf[pos]</code> is
052 * the next byte to be read.
053 */
054 protected byte buf[];
055
056 /**
057 * The index of the next character to read from the input stream buffer.
058 * This value should always be nonnegative
059 * and not larger than the value of <code>count</code>.
060 * The next byte to be read from the input stream buffer
061 * will be <code>buf[pos]</code>.
062 */
063 protected int pos;
064
065 /**
066 * The currently marked position in the stream.
067 * ByteArrayInputStream objects are marked at position zero by
068 * default when constructed. They may be marked at another
069 * position within the buffer by the <code>mark()</code> method.
070 * The current buffer position is set to this point by the
071 * <code>reset()</code> method.
072 * <p>
073 * If no mark has been set, then the value of mark is the offset
074 * passed to the constructor (or 0 if the offset was not supplied).
075 *
076 * @since JDK1.1
077 */
078 protected int mark = 0;
079
080 /**
081 * The index one greater than the last valid character in the input
082 * stream buffer.
083 * This value should always be nonnegative
084 * and not larger than the length of <code>buf</code>.
085 * It is one greater than the position of
086 * the last byte within <code>buf</code> that
087 * can ever be read from the input stream buffer.
088 */
089 protected int count;
090
091 /**
092 * Creates a <code>ByteArrayInputStream</code>
093 * so that it uses <code>buf</code> as its
094 * buffer array.
095 * The buffer array is not copied.
096 * The initial value of <code>pos</code>
097 * is <code>0</code> and the initial value
098 * of <code>count</code> is the length of
099 * <code>buf</code>.
100 *
101 * @param buf the input buffer.
102 */
103 public ByteArrayInputStream(byte buf[]) {
104 this .buf = buf;
105 this .pos = 0;
106 this .count = buf.length;
107 }
108
109 /**
110 * Creates <code>ByteArrayInputStream</code>
111 * that uses <code>buf</code> as its
112 * buffer array. The initial value of <code>pos</code>
113 * is <code>offset</code> and the initial value
114 * of <code>count</code> is the minimum of <code>offset+length</code>
115 * and <code>buf.length</code>.
116 * The buffer array is not copied. The buffer's mark is
117 * set to the specified offset.
118 *
119 * @param buf the input buffer.
120 * @param offset the offset in the buffer of the first byte to read.
121 * @param length the maximum number of bytes to read from the buffer.
122 */
123 public ByteArrayInputStream(byte buf[], int offset, int length) {
124 this .buf = buf;
125 this .pos = offset;
126 this .count = Math.min(offset + length, buf.length);
127 this .mark = offset;
128 }
129
130 /**
131 * Reads the next byte of data from this input stream. The value
132 * byte is returned as an <code>int</code> in the range
133 * <code>0</code> to <code>255</code>. If no byte is available
134 * because the end of the stream has been reached, the value
135 * <code>-1</code> is returned.
136 * <p>
137 * This <code>read</code> method
138 * cannot block.
139 *
140 * @return the next byte of data, or <code>-1</code> if the end of the
141 * stream has been reached.
142 */
143 public synchronized int read() {
144 return (pos < count) ? (buf[pos++] & 0xff) : -1;
145 }
146
147 /**
148 * Reads up to <code>len</code> bytes of data into an array of bytes
149 * from this input stream.
150 * If <code>pos</code> equals <code>count</code>,
151 * then <code>-1</code> is returned to indicate
152 * end of file. Otherwise, the number <code>k</code>
153 * of bytes read is equal to the smaller of
154 * <code>len</code> and <code>count-pos</code>.
155 * If <code>k</code> is positive, then bytes
156 * <code>buf[pos]</code> through <code>buf[pos+k-1]</code>
157 * are copied into <code>b[off]</code> through
158 * <code>b[off+k-1]</code> in the manner performed
159 * by <code>System.arraycopy</code>. The
160 * value <code>k</code> is added into <code>pos</code>
161 * and <code>k</code> is returned.
162 * <p>
163 * This <code>read</code> method cannot block.
164 *
165 * @param b the buffer into which the data is read.
166 * @param off the start offset in the destination array <code>b</code>
167 * @param len the maximum number of bytes read.
168 * @return the total number of bytes read into the buffer, or
169 * <code>-1</code> if there is no more data because the end of
170 * the stream has been reached.
171 * @exception NullPointerException If <code>b</code> is <code>null</code>.
172 * @exception IndexOutOfBoundsException If <code>off</code> is negative,
173 * <code>len</code> is negative, or <code>len</code> is greater than
174 * <code>b.length - off</code>
175 */
176 public synchronized int read(byte b[], int off, int len) {
177 if (b == null) {
178 throw new NullPointerException();
179 } else if (off < 0 || len < 0 || len > b.length - off) {
180 throw new IndexOutOfBoundsException();
181 }
182 if (pos >= count) {
183 return -1;
184 }
185 if (pos + len > count) {
186 len = count - pos;
187 }
188 if (len <= 0) {
189 return 0;
190 }
191 System.arraycopy(buf, pos, b, off, len);
192 pos += len;
193 return len;
194 }
195
196 /**
197 * Skips <code>n</code> bytes of input from this input stream. Fewer
198 * bytes might be skipped if the end of the input stream is reached.
199 * The actual number <code>k</code>
200 * of bytes to be skipped is equal to the smaller
201 * of <code>n</code> and <code>count-pos</code>.
202 * The value <code>k</code> is added into <code>pos</code>
203 * and <code>k</code> is returned.
204 *
205 * @param n the number of bytes to be skipped.
206 * @return the actual number of bytes skipped.
207 */
208 public synchronized long skip(long n) {
209 if (pos + n > count) {
210 n = count - pos;
211 }
212 if (n < 0) {
213 return 0;
214 }
215 pos += n;
216 return n;
217 }
218
219 /**
220 * Returns the number of remaining bytes that can be read (or skipped over)
221 * from this input stream.
222 * <p>
223 * The value returned is <code>count - pos</code>,
224 * which is the number of bytes remaining to be read from the input buffer.
225 *
226 * @return the number of remaining bytes that can be read (or skipped
227 * over) from this input stream without blocking.
228 */
229 public synchronized int available() {
230 return count - pos;
231 }
232
233 /**
234 * Tests if this <code>InputStream</code> supports mark/reset. The
235 * <code>markSupported</code> method of <code>ByteArrayInputStream</code>
236 * always returns <code>true</code>.
237 *
238 * @since JDK1.1
239 */
240 public boolean markSupported() {
241 return true;
242 }
243
244 /**
245 * Set the current marked position in the stream.
246 * ByteArrayInputStream objects are marked at position zero by
247 * default when constructed. They may be marked at another
248 * position within the buffer by this method.
249 * <p>
250 * If no mark has been set, then the value of the mark is the
251 * offset passed to the constructor (or 0 if the offset was not
252 * supplied).
253 *
254 * <p> Note: The <code>readAheadLimit</code> for this class
255 * has no meaning.
256 *
257 * @since JDK1.1
258 */
259 public void mark(int readAheadLimit) {
260 mark = pos;
261 }
262
263 /**
264 * Resets the buffer to the marked position. The marked position
265 * is 0 unless another position was marked or an offset was specified
266 * in the constructor.
267 */
268 public synchronized void reset() {
269 pos = mark;
270 }
271
272 /**
273 * Closing a <tt>ByteArrayInputStream</tt> has no effect. The methods in
274 * this class can be called after the stream has been closed without
275 * generating an <tt>IOException</tt>.
276 * <p>
277 */
278 public void close() throws IOException {
279 }
280
281 }
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